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The objective of this blog is :

- get an idea about Computer Networking

- what is Computer Networking, types of Computer Networking, Networking Devices, Advantages and Disadvantages of Networking.

Computer Networking

1. Introduction to networks

2. Types of network: PAN, LAN, WLAN, MAN, WAN. 

3. Network Devices: modem, hub, switch, repeater, router, gateway, bridges.

4. Network Topologies: Star, Bus, Tree, Mesh.                                                           

5. Introduction to Internet, URL, WWW and its applications - Web, email, Chat, VoIP.

6. Website: Introduction, difference between a website and webpage, static vs dynamic web page, web server and hosting of a website.            

7. Web Browsers: Introduction, commonly used browsers, browser settings, add-ons and plug-ins, cookies.

VPN, Firewall, IP/MAC Address, Data Packet, Rj-45, Ethernet Card

1. Introduction to Networks

Network - Net of  systems ( devices like computers, printers, mobiles, speakers, VDD ) connected in  anyways (through wires or wirelessly)  to work (exchange of info upload and download and resource sharing).

OR

A system containing any combination of computers, computer terminals, printers, audio or visual display devices, or telephones interconnected by telecommunication equipment or cables: used to transmit or receive information. / A computer network is a digital telecommunications network for sharing resources between nodes, which are computing devices that use a common telecommunications technology.

Advantages of Networking

1. Exchange of Information

2. Sharing Resources like –

a.         Peripherals - Laser printers and large storage media are quite expensive. Networks enable

us to share such resources and hence reduce the operational cost of any organization.

b.         Sharing of files and software -  A network enables users to share data files with each other.

For e.g. different departments of an organization may be  separated physically, being at

distant places, but their data could be stored on a central computer which can be accessed

by computers located in different departments. Files and folders can be backed up to local

or remote shares. Software can be installed centrally rather than on each machine which 

proves to be much cheaper than buying licenses for every machine.

c.         Sharing storage - On a network, one can access data from any machine. Hence storage can

be distributed and thus database load can be shared on the network. This even proves to be

cost effective. A file can even have copies on two or three machines.

3. Improving communication - via email, instant messaging, chat rooms, telephone, video telephone calls, and video conferencing.

4. Access to Remote Database  - access any remote database, say for example airline reservations and thereby book tickets.

Other – Faster, Reliable, Cost-effective communication, Centralized Software Management, Flexible Access.

Disadvantages of Networking

1. Threat to Data – Virus / Worms / Hacking

2. Difficult to Set up - Sometimes setting up a network, especially larger networks may turn out to be a difficult task. Larger networks may also be very costly to set up and maintain. Often a specialist/ a team of skilled techies may be needed to run and maintain the network.

Others – Failure of Server, Cable Faults.

Applications of Computer Network - Sharing of resources such as printers, Sharing of expensive software's and database, Communication from one computer to another computer, Exchange of data and information among users via network, Sharing of information over geographically wide areas.

2. Types of Networks

   

Network Name  & Example	Number of People	Devices	Transmission Type		Area
PAN (Personal Area Network)	around an individual person	a mobile / computer / a cell phone and/ or a handheld computing device such as a PDA.	Wired or Wireless Wired PANs - USB and FireWire technologies often link together a wired PAN	Wireless PANs typically use bluetooth or sometimes infrared connections.	Less than 10 meters
LAN (Local Area Network) Organizations Colleges Universities	3 to 100 of computers used by 1000 of people		Wired twisted pair cables and coaxial cables. (Through Switches) Ethernet – is a technology used to provide better communication over LAN (coaxial)	Wireless LAN Wi-Fi Mobile Services	up to a few kilometres
MAN (Metropolitan Area Network) Cable TV network  or  Cable based broadband internet services	buildings in a city / town	Optical Fibres or other digital media	Wired – Provides up- link services to wide area networks (WANs)		30 to 40 km
WAN (Wide Area Network)	often a country or a continent	Commercial and private communication lines to connect computers	1. the different LANs using services such as dedicated leased phone lines, dial-up phone lines, satellite links, high speed fibre optic cables and data packet carrier services.	2. Wide area networking can be as simple as a modem and remote access server for employees to dial into, or it can be as complex as hundreds of branch offices globally linked using special routing protocols	Global

  LAN networks are of various kinds depending upon the type of media, topology, and            protocols they are    using for communication. Local area networks are constructed for small geographical areas within the range of 1-5 km such as offices, schools, colleges, small industries or a cluster of buildings. It is extensively used to design and troubleshoot.

   

Advantages of LAN

Given below are the various advantages of LAN:

• In an office which is connected via LAN network, we can share the hardware and software resources like printers, FAX, drivers and hard-disk as they are on one platform and thus this type of network turns out to be cost-effective.
• As being connected on the network, the offices or firms using the same type of software for job purposes need not purchase separately for each of the host clients as the software can easily be shared with everyone on an equal level.
• LAN network works as a client-server model, therefore data can be stored centrally on one PC called as a server in a network and it can be accessible to all the other client PC’s via LAN. By following this method, we need not store data locally at one single node.
• Communication will be handy and economical by using LAN network.
• Internet cafe owners use the LAN network to provide internet connections to multiple nodes and users connected via a single internet connection. This makes the use of the internet a cost-effective one.

Disadvantages of LAN

The disadvantages of LAN are:

• LAN networks come out to be cost-effective and time-saving, as we can share various resources on one platform. However, the initial installation cost of the network is very high.
• It is having a geographical area limitation and can only cover a small area (1-5 km).
• As it works on a single cable, if it gets faulty then the overall network will stop working. Hence, it needs a full -time maintenance officer called an administrator.
• Crucial Data of offices or factories is saved on a single server which can easily be accessible by all the nodes thus it is having all time data security issues as any unauthorized person can also access the confidential data.

   

Metropolitan Area Network (MAN)

MAN covers a bigger geographical area than LAN Network E.g. cities and districts. It can also be considered as a superior version of the LAN network. As LAN covers only a minor area of the network, MAN is designed to connect a city or two villages together through it.

The area covered by MAN is generally 50-60 km. Fiber optical cable and twisted pair cables are used for connectivity for communication through MAN networks.

MAN can also be considered as a group of one or more LAN networks connected together through a single cable. RS-232, X-25, Frame Relay, and ATM are the common protocol practice for communication in MAN.

 Application of MAN

#1) Various government bodies use MAN network for inter-connectivity between their department’s offices situated at different locations.

For Example, MAN can be used to connect various police stations which are situated within a district or city with each other. The officers can easily communicate with each other and quickly pass on the important data and an urgent message over this network without any need for the Internet connection.

#2) Any private firm can also use a MAN network for inter-connectivity between their offices situated at two different towns of a district. The firm can share resources like data file, images, software & hardware parts etc., with each other. Thus it provides resource sharing over a large distance than the LAN networks.

Advantages of MAN

Given below are the various advantages of MAN:

• It is very efficient and swift for communication over fiber optic cable for interconnection of networks in cities.
• It serves many villages and cities and thus provides great inter-connectivity at a low cost.
• It works on ring or bus topology with a protection link, thus data can be transmitted or received simultaneously over nodes and if one link fails the other will keep the network live.

Disadvantages of MAN

The disadvantages of MAN are:

• Depending upon the distance between two nodes, the cable length required for inter-connection differs every time. Thus greater will be the cable length, the more will be the cost of the network.
• Security is a big concern for this network as for such a big distance anyone can hack the network. We can’t put security at each level of the network, hence it becomes easier for unwanted people to access it for their own benefits.

  

Wide Area Network (WAN)

WAN is widely used in long-distance communication systems.

It covers bigger areas i.e right from a state to a country. Therefore the geographical area it covers is from 100 to several 1000 km. WAN networks are complex in nature, however, they are widely used in mobile communications as they cover up long distances.

 Routers are used in WAN network for communication as they provide the shortest path for communication over long distance using routing tables. Routers also provide a secure and fast rate of transmission.

Different types of data need to be transmitted over the network like image, voice, video and data files. Therefore the routers use packet switching technique for sending and receiving data between nodes. It is not necessary that the device used should be a router only, other devices such as switches, bridges etc., are also used for connectivity.

Routers have routing tables by which they learn the host and destination address for delivery of the data packet and that in turn is the shortest path for transmission. By following this mechanism a source end router will communicate with the far end destination router and exchange the data packets.

Routers and switches have internal memories. Thus when a data packet has arrived at a switch node for delivery, it uses to store and forward the technique for data transmission.

If a media is busy then the node (switch or router) stores the data packets and queues it and when it finds the link free, it then transmits it further. Therefore, packet switching uses data store, queuing and forward technique in the case when the link is found busy.

If the link is free then it just stores and forwards the packet and no queuing is required.

Applications of WAN

#1) Consider the case of an MNC where the head office is situated in Delhi and the regional offices are situated in Bangalore and Mumbai. Here, all are connected through a WAN network.

If HOD’s of corporate office want to share some data with their regional office mates then they can share data (image, video or any data of big size) by saving it on the centralized node which can be accessible by everyone in the organization and is on one single network only.

The centralized server is maintained by an administrator who has the rights to grant access to the users connected to the main server. The administrator will allow sharing only that information which is of the scope of the client nodes.

The rights are reserved for confidential data and only a few higher level authorities of the company will have the rights to access it.

The software testers can also work in this scenario and can share their tools with their colleagues situated hundreds of km away in just a few minutes by using WAN network.

#2) The WAN networks are used for military services. The satellite mode of transmission is used in this setup. Military operations require highly secured network for communication. Thus WAN is used in this scenario.

#3) Railways reservation and Airlines use WAN networks. The client nodes are situated all over the country and are connected to a centralized server node and all are connected to one network. Thus booking can be done from anywhere in the country.

#4) Mobile operators and service providers like NSN or Ericsson use WAN network to provide mobile services in a particular circle. Different circles of a country are also connected with each other through WAN networks. The connections are made through routers and switches using higher bandwidth STM links.

#5) The WAN network also works in master-slave scenario and main & protection link topology.

If one link fails then the data transmission will keep moving smoothly by a protection link. By master-slave scenario, if the master device fails then the slave will act as a master and will take all the responsibilities for data packet transmission without any delay and failure.

Advantages of WAN

Given below are the various advantages of WAN:

• It connects various cities and states with one another. Hence, large scale industries can be connected to one single network.
• N number of nodes can be connected over this network for sharing software.
• As routers are used for sending and receiving the end of the network, the rate of transmission is very high even if we send large sized files of more than 10 MB.
• All users connected via WAN will remain in synchronization with each other at all the time, therefore, there will be no chances of communication gap between them.
• The users can share the hardware like printers, hard-disk etc. with each other and there is no need to buy a separate connection for internet as all type of communication can be done within as they are being on one network only.

Disadvantages of WAN

The disadvantages of WAN are:

• Confidential and important data is shared over a long distance, hence there are chances for unwanted people to try to interrupt and hack the data. Therefore there is always a need to purchase a security firewall for the network to protect it from the outside threats.
• Set-up of WAN network is complex and costly.
• As WAN network is spread over a very large distance, we need to deploy a local administrator at every intermediate point to ensure its maintenance and fault control.
• Local monitoring of such wide networks is not sufficient enough to maintain it properly. Therefore, some companies, like mobile operators will set up a NOC and purchase a GUI based centralized monitoring tool for operation and maintenance purpose. This will cost them a lot of manpower and money for running it smoothly.

3. Networking Devices

A modem (Modulator - Demodulator) is a peripheral device that enables a computer to transmit data over, telephone or cable lines. 

•       Allow computers to communicate over a telephone line

•       Enable communication between networks or connecting to the world beyond the LAN

It modulates an analogue carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. This is why modem is an acronym of MOdulator/DEModulator. The goal of this process of modulation - demodulation is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data. 

Types of Modem

1. External Modem - is like an adapter which has two end. One end is attached to the CPU and the other end is attached to the telephone jack, is easy to set-up.

2. Internal Modem - is a small chip (circuit chip) which is placed on the motherboard or is attached to it through expansion slot. Set-up is difficult and is importable.

Repeater - A repeater is a device that works with signals on the cables to which it is connected. The weakened signal appearing on the cable is regenerated and put back on the cable by a repeater. These signals can travel a specified distance (usually about 100 m). 

Or better, it is an analog device that receives a signal , amplifies it and then retransmits it on the network so that the signal can cover longer distances.

Ethernet Card

Ethernet card, also known as Network Interface Card (NIC card in short) is a network adaptor (a circuit board mounted on the motherboard) used to set up a wired network. It acts as an interface between computer and the network. 

Ethernet cards can support data transfer between 10 Mbps and 1 Gbps (1000 Mbps). Each NIC has a MAC address, which helps in uniquely identifying the computer on the network. 

RJ-45 - short form of Registered Jack - 45 , is an eight wired connector that is used to connect computers on a local area network(LAN), especially Ethernet. RJ-45 connectors look similar to the RJ-11 connector used for connecting telephone equipment, but they are somewhat wider. 

A  Hub is a device commonly used to connect segments of a LAN. The hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

A Switch is a smart Hub because it allows different nodes (through ports) of a network to communicate directly with one another ( not with all the ports) in a smooth and efficient manner. Unlike hubs, network switches are capable of inspecting data packets as they are received, determining the source and destination device of each packet, due to the MAC (Media AccessControl) Address reading capability and forwarding them appropriately

This prevents traffic overloading on the network.

A LAN switch creates a series of instant networks that contain only the two devices communicating with each other at that particular moment.

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